1. Field of the Invention
The present invention relates to a moving target detecting system and a moving target detecting method.
2. Description of the Related Art
Various proposals have been put forth with respect to a moving target detecting system which is suitable for tracking other flying airplanes, etc. if loaded on a guided missile, a military airplane, etc., for example, and a moving target detecting method for use in the moving target detecting system.
As an example, in the event that the guided missile tracks other moving airplanes, such a system has been known that a image pick-up device such as CCD camera is loaded on the guided missile to pick up a spatial domain including a target airplane as a still image, and then an image pattern of the airplane can be grasped by scanning the still image as a whole in unit of pixel to thus detect the presence of the moving target and its location.
More particularly, the system has been known wherein, for example, brightness average of the resultant still image is calculated, and then the brightness in respective pixels of the still image are compared with each other to thus identify/extract the image of the target whose brightness is considerably different from a brightness average level, so that the target can be detected by removing a background such as cloud, land, etc. from the picked-up image.
However, such system needs a plenty of processing time to discriminate/extract the moving target from the overall still image since one frame of the overall still image in the picked up area is scanned in unit of pixel to thus carry out the image processing for profile pattern recognition.
Besides, another system has been proposed wherein, for example, processing gates are provided in the vicinity of the target which has been extracted once to improve a processing speed and then an input signal level to an image processor can be adjusted by calculating brightness average within the processing gates.
Meanwhile, if the image pattern of the background having the brightness which is resemble and confusing to that of the target, e.g., the images of land and cloud, in addition to the image of the target exists in the picked-up image, difference in brightness between the moving target as an object and the background other than the moving target, i.e., contrast between them has been made relatively vague because of influence of the sunlight, etc., otherwise the contrast has dispersed over the screen as a whole although the contrast is sharp. For this reason, such a problem has been arisen that it is not easy to distinguish the target from the background precisely by identifying the target only and thus to detect the target quickly. Even if the processing gates are provided, the brightness average level becomes an inadequate value, for example, when the background image pattern enters into the processing gates. Therefore, such situation has occurred similarly.